It has become common practice today to use disposable diapers with infants and incontinent people. Disposable diapers generally have a rectangular or hour glass shape and comprise an absorbent batt material sandwiched between an outer flexible polyethylene backsheet and an inner flexible, polypropylene or polyester nonwoven frontsheet. The outer backsheet typically, but not necessarily, is water-impervious to prevent voided liquid absorbed into the absorbent batt material from striking through the diaper and soiling the infant's adjacent clothing or bedding. The inner frontsheet on the other hand is water-pervious to permit the voided liquid to pass therethrough into the absorbent batt material to maintain the infant in a dry, comfortable state.
It is also well known and common practice in manufacturing disposable diapers to rely upon tape-tab fasteners as means for fastening the diapers about infants. The safety advantages and practicality of tape-tabs, rather than pins, is self evident. However, there are several shortcomings associated with their use. One major shortcoming lies in the loss or lack of tape adhesion between the tape-tab fasteners and backsheets following the original closures preventing the tape-tab fasteners from being positioned or repositioned on the backsheets. This shortcoming becomes immediately apparent when users, such as nurses or parents, attempt to separate the tape-tab fasteners from the diapers to inspect for soiling and refasten them following their inspection or when the diapers fall off due to the failure of tape-tab fasteners.
Some backsheet materials available heretofore for disposable diapers have very poor tape adhesion, i.e., the pressure-sensitive adhesives of the tape-tab fasteners do not or cannot adhere to the backsheets, making positioning or repositioning very cumbersome, if not virtually impossible. Unfortunately, this results in unsoiled diapers being discarded and wasted following routine inspection or childrens' participation in the toilet-training ritual. This lack of reusability not only is inconvenient but also expensive because of the rising costs associated with disposable diapers.
In one attempt to solve the refastening problem, U.S. Pat. No. 4,163,077, issued to Antonsen et al. on July 31, 1979, proposes to formulate the pressure-sensitive adhesive of the tape-tab fasteners with a rubbery block copolymer tackified with a combination of certain liquid and solid tackifiers to improve adhesion and shear properties when the backsheet is contaminated with foreign substances, such as talcum powder.
While U.S. Pat. No. 4,163,077 reflects one attempt, there have been other attempts made in the past to solve the repositioning problem. Unfortunately, they have attempted to solve such problem by modifying either the tape-tab fasteners, the pressure-sensitive adhesives used therewith or by coating the tape-tab fastener bonding regions located on the backsheets. These closure systems have the disadvantages of restricting the disposable diaper manufacturers to a particular tape-tab fastener arrangement, a particular pressure-sensitive adhesive formulation or added manufacturing steps, and forcing them to select only those backsheets that are coated at the bonding regions or are compatible with such arrangements or pressure-sensitive adhesive formulations in order to produce an effective repositionable closure system. Such methods also have the disadvantage of adding to the cost of manufacturing disposable diapers.
Consequently, there is a definite need for a repositionable yet inexpensive and flexible closure system that is not restricted to a particular tape-tab fastener arrangement, pressure-sensitive adhesive formulation or coated backsheet, that has good tape adhesion when the diapers are initially closed, and that does not lose substantial tape adhesion upon repeated use of the tape-tab fasteners following occasional inspection for soiling or childrens' participation in the toilet-training ritual permitting unsoiled diapers to be reused.